This invention relates generally to flexible door structures and is particularly directed to lightweight, pliable roll-type overhead doors.
Roll-type doors are frequently used in industrial installations to isolate two rooms or the inside of a building from the outside environment while permitting transit between the two rooms or either out of or into the building as desired. These roll-type doors are generally mounted on a pair of vertically aligned tracks and are securely coupled at an upper end portion thereof to a roller which is rotated in a first direction to lower the door or in a second direction to retract the door. The roller is typically mounted immediately above the doorway and generally includes an electric motor for rotationally displacing the roller. Doors of this type have generally been comprised of a plurality of rigid hingedly interconnected metal panels which can be wrapped around the roller when retracted for storage while providing a rigid door structure of high strength when lowered in position in the doorway.
Recent developments in the area of roll-type doors have given rise to another type of door comprised of a pliable sheet-like structure which frequently is transparent and is adapted for rapid displacement between the retracted, rolled up configuration and the lowered, extended configuration. These doors are typically comprised of a high strength plastic material such as polyvinyl chloride only limited success in maintaining the door in a laterally stretched condition so that it remains extended from one side of the doorway to the other. The absence of lateral rigidifying means in existing pliable, lightweight roll-type doors has limited their usefulness in environments where wind is a factor or where a large pressure differential exists between the two rooms separated by the door.
Some prior art doors of this type incorporate trolleys coupled to respective lateral-edge portions of the pliable door which are mounted in and displaceable within respective tracks positioned adjacent to lateral portions of the door. While this trolley/track arrangement maintains the pliable door laterally taut, such arrangements substantially increase the complexity and cost of the door installation.
The present invention overcomes the limitations of the prior art by providing structural means for maintaining a lightweight, pliable, roll-type door in a laterally stretched condition across a doorway without the use of a trolley/track combination. The present invention contemplates one or more windstraps positioned in spaced relation along the length of the door and extending substantially the width thereof so as to maintain the door generally flat even when subjected to lateral loading on one surface thereof such as due to wind or a pressure differential. (PVC) and may be displaced from the open to the closed position, or vice versa, in just a few seconds. As this type of door lacks the structural strength of the aforementioned multi-section hinged roll-type door, roll-type doors comprised of a single pliable sheet-like member are intended primarily for environmentally isolating two adjacent rooms or the inside of a building from the environment outside rather than for providing security by preventing transit through a doorway. A rapidly displaced overhead roll-type door having good insulating characteristics is particularly desirable from an energy conservation standpoint where there is a large differential between inside and outside temperatures.
A primary difference between the single sheet, pliable roll-type doors and the aforementioned multi-section, hingedly interconnected rigid roll-type doors is that the former require tensioning means coupled to the lower end portion of the door in order to maintain the door in a taut condition so as to prevent lateral displacement of the door, while in the latter installation the considerable weight of the door maintains the door in a planar configuration during raising and lowering. Pliable roll-type door tensioning arrangements typically include various combinations of springs, pulleys and weights to exert a downward force on the lower edge portion of the door so as to maintain it generally planar across the doorway when it is extended. Thus, while the prior art has provided for stretching pliable overhead roll-type doors in a generally vertical direction to maintain the door in a flat configuration, prior art approaches have met with